1. Technical Field
The present invention relates to an apparatus for storing an electric energy and a method of manufacturing the same, and more particularly, to an apparatus for storing an electric energy having an angular structure of an improved resistance characteristic and a method of manufacturing the same.
2. Description of the Related Art
In general, apparatuses for storing an electric energy include batteries and capacitors.
Capacitors are generally classified into electrostatic capacitors, electrolytic capacitors, and electrochemical capacitors. Electrochemical capacitors are referred to as super capacitors and are electric energy storing apparatuses that store and supply the electric energy by using a movement of ions caused by an electrochemical reaction between electrodes and electrolytes, which have recently received much attention as new concept electric energy storage power sources cable of quickly storing or supplying a great amount of energy owing to their excellence in an energy density and an output density compared to conventional electrolytic capacitors and secondary batteries.
Such super capacitors have a very high capacitance, can be quickly charged and discharged, and have a high charging and discharging efficiency and a semipermanent cycle lifespan, by using a charging phenomenon due to a simple movement of ions to an interface between electrodes and electrolytes or a surface chemical reaction.
Since the above super capacitors have a characteristic of supplying a great amount of current within a short time, a market tends to increase to systems requiring an independent power supply apparatus, systems for adjusting an overload that instantly occurs, and energy storing apparatuses. In particular, since the super capacitors have excellent energy input and output compared to secondary batteries, the super capacitors are expected to have a variety of applications as a back-up power source that is an auxiliary power operating at an instant blackout, a pulse power source of a portable mobile communication device, and a high output power source of a hybrid electric car. Also, the super capacitors have excellent charging and discharging efficiency or lifespan compared to secondary batteries, relatively wide available temperatures and voltage ranges, need no maintenance and repair, and are advantageously environment-friendly, and thus being reviewed as secondary battery substitutes.
The above super capacitors are manufactured as two types of cylindrical and angular shapes. The angular super capacitors are mainly used since they have higher space efficiency than the cylindrical super capacitors when a module is manufactured.
In the conventional angular super capacitors, an electrode stack is manufactured by stacking electrodes on which an active material is coated and electrodes. A single super capacitor is manufactured by using a single of the above-manufactured electrode stack or by combining a plurality of the above-manufactured electrode stacks according to a designed capacity. The single super capacitor is manufactured by binding leads of electrodes, performing ultrasonic welding or cold welding on the leads, performing a rivet on an external terminal unit formed in a case, and forming an external terminal.
In the above-manufactured super capacitors, as shown in FIG. 5A, when current is applied, charges in the electrodes may move to the leads connected to the terminals, and a resistance component may occur due to the leads of limited sizes. Also, since the leads of electrodes are bound to connect the leads to the external terminal using the rivet, a contact resistance occurs, and heat is generated at a part connected to the external terminal when a high current is charged and discharged, which causes a problem of promoting deterioration of super capacitors.